Ann Arbor (Michigan), Aug 23 - Despite mounting public health concerns about obesity and persistent social pressures dictating that slim is beautiful, young women in their '20s consistently exercise less than young men.

And young black women showed significant declines in exercise between 1984 and 2006, according to a University of Michigan study.

The study is one of the first to analyze long-term patterns in weight-related activities and to assess how these patterns vary by gender, race and ethnicity, and socioeconomic status.

The disparities in health behaviours, the study reveals, are consistent with disparities in the prevalence of obesity, particularly among women, according to Philippa Clarke, lead author of the study and a researcher at the U-M Institute for Social Research (ISR).

The study is based on data obtained every two years from 17,314 men and women who were aged 19 to 26 between 1984 and 2006.

For the study, the researchers measured how often participants reported eating breakfast, and eating at least some green vegetables and fruit; how often they exercised vigorously (jogging, swimming, or calisthenics); how often they got at least seven hours of sleep, and how much television they watched on an average weekday.